In prior art tire vulcanization methods, for shaping a green tire, the outer circumference of a bladder is made in tight contact with the inner circumference of the green tire by setting the green tire is in a center mechanism of a vulcanizer and inflating the bladder of the center mechanism with a pressurized fluid.
Then, the bladder supplied with a high-temperature and pressure fluid is pressed into the inner circumference of the green tire held in a container of the vulcanizer, whereby the green tire is vulcanized by heat from the bladder and the container.
However, such a prior art tire vulcanization method has a problem that since the green tire is set in the center mechanism of the vulcanizer for shaping, pre-vulcanization processing takes a long time, causing a reduction in work efficiency.
In view of solving the above problem, in prior art there has been proposed a tire vulcanizer disclosed in Japanese Laid-open Patent Application Publication No. 2002-178333 which is configured to shape a green tire with a shaping unit outside a vulcanizer body and vulcanize the shaped green tire while the shaping unit is set in the vulcanizer body.
This prior art tire vulcanizer includes a shaping unit for off-line setup, that is, mounting a green tire outside the vulcanizer body and shaping the green tire.
Thus, the use of the shaping unit has an advantage of improved work efficiency since just setting in the vulcanizer body the green tire shaped outside enables immediate start of vulcanization.
However, for shaping the green tire in the shaping unit, it is necessary that the upper and lower clamp rings can be positioned at a bladder extended position at which they are distanced away from each other so that an outer diameter of the bladder is to be smaller than an inner diameter of the green tire and at a shaping position at which they approach each other so that the outer circumference of the bladder is to be made in tight contact with the inner circumference of the green tire.
In this regard, the prior art tire vulcanizer is configured to include a fastener ring in the upper clamp ring, and positions the upper and lower clamp rings by rotating the fastener ring by a motor to thereby engage the fastener ring with the lower clamp ring.
However, there is a problem that a complex fastening structure is needed to rotate the fastener ring by the motor to join the upper and lower clamp rings at the shaping position.
In view of solving the above problem, the present invention aims to provide a tire vulcanizer in which the upper and lower clamp rings can be positioned at the shaping position easily and smoothly with a simple engagement structure.